Abstract

The HadISSTI sea surface temperature data set is examined for two contrasting areas: the Chagos Archipelago, central Indian Ocean which has a small (similar to3 degreesC) annual temperature fluctuation, and Abu Dhabi in the southern Arabian Gulf whose annual air temperature fluctuation of similar to24 degreesC is the largest known for coral reef habitats. The HadISST1 data are shown to match air temperature records closely, both in terms of annual moving averages and residual analysis. Temperatures in 1998 caused massive mortality of corals in the Indian Ocean: sea surface temperature (SST) values causing this were 33.8 degreesC in the Arabian Gulf at a time when average daily air temperature was over 40 degreesC, while in Chagos the SST lethal to corals was 29.8-29.9 degreesC, when air temperatures peaked at about 31 degreesC. The HadISST1 record was searched back to 1870 for previous abnormal peaks: one of 29.7 degreesC was found for Chagos SST in 1972, though this did not cause coral mortality. Analysis of 12-month running means of the residuals from the annual cycle show that, between 1870 and 1999, the largest SST deviations occurred between October 1997 and May 1998 in Chagos and between August 1998 and July 1999 near Abu Dhabi. The event of 1998-1999 was the largest in these regions for at least 130 years. SSTs have risen over the last three decades at rates of about 0.22degrees or 0.23degrees per decade in both locations. Crown Copyright (C) 2002 Published by Elsevier Science Ltd. All rights reserved.